<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let arr = [
            ["小明", "18"],
            ["小刚", "18"]
        ];
        
        let newArr = arr.flatMap((item, index) => {
            item = item.filter((item, index) => index === 0)
            return item;
        });

        console.log(newArr); // ["小明", "小刚"]
    </script>
</body>
</html>